The Universal Terrestrial Radio Access Network (UTRAN) of the Long-Term Evolution (LTE) project, also denoted E-UTRAN, as standardized in Rel-8 of the 3rd Generation Partnership Project (3GPP) specification, supports transmission bandwidths spanning a contiguous spectrum portion. In order to meet requirements for International Mobile Telecommunications-Advanced (IMT-Advanced) standards, 3GPP has initiated work on LTE-Advanced. One aspect of LTE-Advanced is support for bandwidth aggregation across a larger spectrum range. Another aspect of LTE-Advanced is to allow for backward compatibility.
To allow for an expanded bandwidth for data communication to and from a mobile terminal, LTE-Advanced systems may be operable to aggregate contiguous or non-contiguous spectrum portions and thereby—from a baseband point of view—allocate a large system bandwidth. Carrier aggregation, as defined by 3GPP, is non-contiguous if two frequency resources are separated by a frequency gap. Carrier aggregation without a frequency gap is called contiguous. In the aggregation example illustrated in FIG. 1, a pair of contiguous frequency resources of 10 MHz and 20 MHz are aggregated together with a non-contiguous frequency resource of 20 MHz, resulting in an aggregated bandwidth of 50 MHz available for data communications.
The benefit of aggregating frequency resources across a spectrum is that it becomes possible to generate a sufficiently large bandwidth for supporting data rates up to (and above) 1 Gbit/s, a throughput requirement for a “4G” (IMT Advanced) system. Furthermore, aggregating across the spectrum also makes it possible to adapt the spectrum portions to the current situation and geographical position, making such a solution very flexible.
A straightforward evolution of current cellular systems, like LTE, to support non-contiguous spectrum is to introduce a multi-carrier concept. That means that each frequency resource (or spectrum “chunk”, see FIG. 1) represents a “legacy LTE” system and a “4G” mobile terminal is capable to receive multiple number of 3GPP Release 8 LTE carriers (called component carriers) of different bandwidths transmitted at different carrier frequencies.
Through the above-described aggregation techniques, LTE-Advanced systems may be operable to transmit and/or receive on multiple frequency resources which may be contiguous or on different portions of the spectrum. In a system utilizing multiple frequency resources, it is not optimal, in terms of power consumption (for example, for a battery operated mobile terminal) to receive control signaling on all or across multiple frequency resources. For example, a mobile terminal may be idle or transmitting only voice such that only the capacities of a single frequency resource may be required. When a single frequency resource provides adequate throughput for data to/from the mobile terminal, transmitting across two or more frequency resources will be wasteful, requiring, for example, unnecessary scheduling across frequency resources and increased power consumption.
Therefore, the mobile terminal may be configured to transmit and/or receive control information and data on the selected frequency resource only. When receiving/transmitting data amounts requiring a larger throughput or greater speed, the mobile terminal may receive/transmit data and control signaling on other available frequency resources as well as on the selected frequency resource. The concept of using a selected frequency resource for control signaling may be referred to as anchor, or primary, component carrier use, and the selected frequency resource for a mobile terminal may be referred to as the anchor component carrier for this mobile terminal. Anchor component carrier and further component carriers are sometimes also referred to as primary (component) carrier and secondary or supplementary (component) carriers, respectively.